homepage/gatsby-node.js

const path = require(`path`)

exports.createPages = async ({ actions, graphql, reporter }) => {
  const { createPage } = actions

  const siteTemplate = path.resolve(`src/templates/siteTemplate.js`)

  const result = await graphql(`
    {
      allMdx(limit: 1000, filter: { fields: { source: { eq: "pages" } } }) {
        edges {
          node {
            frontmatter {
              path
              title
              edit
            }
          }
        }
      }
    }
  `)

  // Handle errors
  if (result.errors) {
    reporter.panicOnBuild(`Error while running GraphQL query.`)
    return
  }

  result.data.allMdx.edges.forEach(({ node }) => {
    createPage({
      path: node.frontmatter.path,
      component: siteTemplate,
      context: {}, // additional data can be passed via context
    })
  })
}

exports.onCreateNode = ({ node, getNode, actions }) => {
  const { createNodeField } = actions

  if (node.internal.type === `Mdx`) {
    const value = getNode(node.parent).sourceInstanceName
    createNodeField({
      node,
      name: `source`,
      value,
    })
  }
}

exports.createSchemaCustomization = ({ actions }) => {
  const { createTypes } = actions
  const typeDefs = `
    type Mdx implements Node {
        frontmatter: Frontmatter
    }

    type Frontmatter {
        edit: String
    }
  `
  createTypes(typeDefs)
}